Safety joint



R. TREESE SAFETY JOINT June 11, 1968 Filed Sept. 12, 1966 4, K fl'lwz,

ATTORNEY INVENTOR A0) 7RJ 3,387,863 SAFETY JOINT Roy Treese, Dallas,Tern, assignor to Bresser Industries, Inc., Daiias, Tern, a corporationof Delaware Filed Sept. 12, 1966, Ser. No. 578,565 6 Qiairns. {CL285-2.)

ABSTRAQT OF THE DISCLUEBURE This invention relates generally to improvedsafety joints connectable in a string of tubing or the like arranged tobe disposed in a well bore. More particularly, but not by way oflimitation, this invention relates to an improved safety joint having afrangible portion that separates upon the application of a predeterminedtensile force thereto, permittin separation of the tubing string.

In treating oil and gas wells, it is frequently necessary to set a wellpacker at a location deep within the well bore. One method utilized toplace the packer in the desired position in the well bore and to set thepacker therein is to connect the packer to the lower end of a tubingstring that extends from the surface of the well. The string alsoprovides the means for setting the packer after it has reached thedesired depth.

Occasionally, the packer becomes stuck in the well bore to the extentthat the packer cannot be released and retrieved on the tubing string.When this occurs, the tubing string must be released from the packer sothat an overshot or other fishing tool may be lowered into the well boreto remove the packer. To permit separation of the tubing string from thepacker, it is a common practice to connect a safety joint between thelower end of the tubing string and the upper end of the packer wherebyseparation thereof can be easily accomplished.

Various types of safety joints have been constructed in the past topermit the separation of the tubing string from the packer. Some haveincluded relatively rotatable parts retained in a fixed position by oneor more shear pins that shear or part upon the application of a torqueexceeding their shear strength. Other types have included either J-slotsor threaded connections that also require rotation of the tubing stringrelative to the packer.

As is well known to those skilled in the art, it is dangerous to rotatethe tubing string due to the possibility of either unscrewing one of themany threaded joints in the tubing string or due to the possibility oftwisting off the tubing string. In an effort to overcome the undesirablerotation, safety joints have been constructed utilizing a purelytensional force to separate the safety joint. In this type of joint, thewall thickness is reduced in a relatively small area providing afrangible portion wherein such separation will occur upon theapplication of the tensile force.

While this type of joint has been relatively successful, three primarydifiiculties have been encountered. Firstly, in most treating operationsinvolving the use of such equipment, the tubing string is tested withrelatively high internal pressures and the frangible portions are notusually of sufficient thickness to withstand the test and/or tatesPatent ice treating pressures. To alleviate this problem, the generalpractice has been to construct the joint 50 that the fluid underpressure is on both sides of the frangible portion thereby eliminatingthe fluid pressure differential across the frangible portion.

Secondly, and particularly when the fluid pressure is applied on bothsides of the frangible portion to afford pressure equalization, thefrangible portion is subjected to a tensile force resulting from saidfluid pressure. It is therefore not possible to predict the precisetensile force necessary to separate the safety joint unless the preciseinternal fluid pressure is known when the joint is manufactured andsufiicient wall thickness is left to compensate for such pressure.Generally, the testing or treating pressures are not known in advance.

Thirdly, the frangible portion is subject to compressive loads placed onthe tubing string. Manifestly, such loads, if sufficiently great, willbuckle the frangible portion if it is not supported and most tensiontype joints are of relatively complex structure whereby such compressiveloads are carried through the body of the joint avoiding the applicationof the loads to the frangible portion.

Summary of the invention This invention provides an improved safetyjoint connectable in a string of tubing and providing for the separationof the tubing upon the application of a predetermined tensile force, thesafety joint comprising: a unitary tubular body member having endportions arranged for connection with the tubing string; and, an annulargroove encircling the exterior thereof intermediate said portionsforming a frangible portion thereon, the frangible portion having apredetermined tensile strength whereby the safety joint will part in thefrangible portion when a tensile force is exerted on the tubing stringexceeding the strength of the frangible portion.

One object of the invention is to provide an improved safety joint thatwill separate upon the application of a predetermined tensile force andthat requires no rotation for separation.

A further object of the invention is to provide an improved safety jointwherein the joint will part upon the application of a tensile forceexceeding the predetermined tensile strength of the safety joint andthat is supported against compressive loads.

Another object of the invention is to provide an improved safety jointof the tension type that is unaffected by internal pressure in thetubing string or by compressive loads placed on the tubing string.

A still further object of the invention is to provide an improvedtension type safety joint that will separate cleanly and leave no debrisor junk in the well bore after separation.

Still another object of the invention is to provide an improved tensiontype safety joint that can be easily and economically manufactured.

The foregoing and additional objects and advantages of the inventionwill become more apparent as the following detailed description is readin conjunction with the accompanying drawings wherein like referencecharacters denote like parts in all views and wherein:

FIGURE 1 is a vertical cross-sectional view of a well bore illustratinga tubing string and packer disposed therein that are connected by asafety joint constructed in accordance with the invention;

FIGURE 2 is an enlarged cross-sectional view taken substantially alongthe line 2-2 of FIGURE 1 and showing the structure of the safety jointof FIGURE 1 in more detail; and

FIGURE 3 is an enlarged cross-sectional view similar to FIGURE 2, butillustrating the safety joint after the joint has been parted.

Referring to the drawing and to FIGURE 1 in particular shown therein isa cased well bore generally designated by the reference character 10, apacker 12 located in the well bore, a safety joint generally designatedby the reference character 14 connected with the upper end of the packer12, and a string of tubing 16 connected with the safety joint 14 andextending upwardly through the well bore to the surface (not shown) ofthe well. The packer 12 is illustrated as being fixed in the well bore10 by a plurality of slips 18 that are expanded into holding engagementwith the casing disposed in the well bore 1%. The tubing string 16 ismade up of a plurality of sections of tubing 20 that are threadedlyconnected in end-to-end relationship as indicated by the box and pinjoint 22.

FIGURE 2 illustrates the structure of the safety joint 14 in greaterdetail. As shown therein, the safety joint 14 includes a tubular body 24having a bore 26 extending therethrongh. Threads 28 are formed in thebore 26 in the upper end portion of the tubular body 24 threadedlyconnecting the safety joint 14 with the lowermost section 20 of thetubing string 16. Threads 36 formed on the exterior of the lower endportion of the body member 24 threadedly connect the safety joint 14with the upper end of the packer 12.

An annular groove 32 is provided in the exterior of the body 24 forminga frangible portion 33 and a downwardly facing annular shoulder 34thereon. A second annular groove 36, spaced from the annular groove 32,encircles the body 24 forming an upwardly facing annular shoulder 38thereon. As is apparent in FIGURE 2, the frangible portion 33 has arelatively small cross-sectional area so that the safety joint 14 willpart therein as will be described more fully hereinafter.

An annular flange 49 is provided on the body 24 between the annulargrooves 32 and 36. For reasons that will become more apparenthereinafter, the outer diameter of the annular flange 40 is less thanthe outer diameter of the body 24.

Disposed in close fitting relationship in the grooves 32 and 36 are apair of support members 42. The support members 42 are preferablyhemi-cylindrical in shape so that they can be easily inserted into thegrooves 32 and 36, but they may be constructed in other segmented formsif desired.

It will also be noted that the support members 42 are each provided withan inwardly directed arcuate flange 44 that fits closely within theannular groove 32 and a second inwardly directed arcuate flange 46 thatfits closely within the annular groove 36. The length of each of thesupport members 42 is substantially the same as the combined lengths ofthe grooves 32 and 36 and the flange 40 whereby the ends thereof are insupporting engagement with the downwardly facing annular shoulder 34 andthe upwardly facing annular shoulder 38 located on the body 24. Thus,the support members 42 carry any compressive loads exerted on the body24, preventing compressive buckling of the frangible portion 33.

In the preferred form of the safety joint 14, the support members 42 areconstructed to the same dimensions for a given size of the safety jointregardless of the desired tensile strength of the frangible portion 33,that is, regardless of the desired parting strength. This is possiblesince the diameter of the bore 26 can be varied to vary thecross-sectional area of the frangible portion 33 and, thus, vary theparting strength thereof.

The diameter of the bore 26 can be varied to maintain a constant tensilestrength for the frangible portion 33 when different lots of materialare used in forming the body 24. Manifestly, the tensile strength of thematerial varies to some extent despite the manufacturers attempt tomaintain the strength constant.

Also, varying the diameter of the bore 26 provides for the constructionof a frangible portion 33 of a desired parting strength to meet specialsituations. Again, it should be pointed out that such parting strengthscan be attained even though the support members 42 remain the same size.Thus, the manufacturing and inventory problems connected with the safetyjoint 14 are reduced to a minurnum.

The outer diameter of a portion of the body 24 has been reduced forminga downwardly facing annular shoulder 43 thereon. A sleeve 50 encirclesthe reduced diameter portion of the body member 24 in close fittingrelationship having its upper end abutting the annular shoulder 48 andhaving the lower end thereof connected to the body member 24 between theannular groove 36 and the lower end portion by welding, as illustratedby the reference character 52, or by another suitable means.

The sleeve 50 completely covers the grooves 32 and 36 and is inengagement with the exterior of the support members 42 thereby retainingthe support members 42 in the grooves 32 and 36. The sleeve 5% alsoserves to resist bending of the safety joint .14 and aids in supportingcompression loads exerted thereon through its engagement with theshoulder 48.

Operation To utilize the safety joint 14, the lower end thereof isthreadedly connected with the upper end of the packer 12 and the upperend thereof threadedly connected with the lowermost section of tubing20. The packer 1'2, safety joint 14, and lowermost section of tubing 20are then lowered into the well bore 10. The desired number of additionalsections of tubing 20 are connected in end-to-end relationship by thebox and pin joints 22 until the packer 20 has reached the desired depthin the well bore 10.

After reaching the desired depth, the packer 12 is actuated through thetubing string 16 to set the packer 12 in the casing. Assuming that thepacker 12 becomes stuck and cannot be retrieved from the well bore 10,an upwardly directed or tensile force is exerted on the tubing string 16through apparatus (not shown) located on the surface thereby exerting atensile force on the safety joint 14.

When the tensile force exerted on the tubing string 16 exceeds apredetermined value, the frangible portion 33 of the safety joint 14parts as illustrated in FIGURE 3, permitting retrieval of the tubingstring 16 and the upper portion of the body 24 of the safety joint 14.The lower portion of the body 24, sleeve 50, support members 42, and thepacker 12 are left in the well bore 10.

As clearly illustrated in FIGURE 3, the support members 42 are retainedin the second annular groove 36 between the sleeve 56 and the annularflange 49 that extends outwardly from the tubular body 24 into therecess in the support members 42 located between the inwardly directedflanges 44 and 46 thereon. Thus, there is no junk or debris left in thewell bore 10 as a result of the parting of the safety joint 14 thatmight interfere with future operations therein.

From the foregoing detailed description of the structure and operationof the safety joint .14, it can be appreciated that the only movement ofthe tubing string necessary to part the safety joint 14 is in the upwarddirection, that is, only a tensile force need be exerted thereon. Thus,and even though the safety joint 14 is sufiiciently strong to permitactuation of the packer 12 by compression, rotation or tension, it isnot necessary to rotate the tubing string 16 to part the safety joint14.

It will also be apparent from the foregoing, that the smoothconstruction of the bore 26 avoids the imposition of tensile forces onthe frangible portion 33 that may result from fluid pressure in thetubing string 16. This is an important feature due to the fact thatfrequently pressures in the neighborhood of 10 to 15 thousand pounds persquare inch may be utilized in either testing the tubing string 16 or inthe performance of certain treating operations in the well bore 10. Thesleeve 50 and the support members 42 support the frangible portion 33against outward deformation resulting from such pressure, whereby thefangible portion 33 is completely free from the effect of any pressurecarried within the tubing string 16. Thus, it is possible to predict theprecise tensile force necessary to separate the fangible portion 33.

Furthermore, an examination of FIGURES 2 and 3 clearly demonstrates thatthe safety joint 14 is of a relatively simple construction that may bequickly and economically constructed utilizing normal manufacturingprocedures and equipment.

The single embodiment described herein is presented by Way of exampleonly and it will be understood that many changes and modifications canbe made thereto without departing from the spirit of the invention orthe scope of the annexed claims.

What I claim is:

1. In a string of well tubing or the like adapted to be disposed in awell bore and to carry fluid under pressure, a safety joint connectablein said tubing providing means for the separation of the tubing uponapplication of a predetermined tensile force, said safety jointcomprismg:

a unitary tubular body member having first and second end portionsarranged for connection with the tubing string, and an annular grooveencircling the exterior thereof intermediate said end portions forming afrangible portion thereon, said frangible portion having a predeterminedtensile strength whereby said safety joint will part in said frangibleportion when a tensile force is exerted on said tubing string exceedingthe strength of said frangible portion; and support means at leastpartially disposed in said annular groove, said support means engagingsaid tubular body member in said groove to support said frangibleportion against deformation by the fluid under pressure and againstdeformation resulting from compressive loads placed on said tubingstring thereby avoiding compressive buckling of said frangible portion.

2. The safety joint of claim 1 wherein said tubular body member alsoincludes a substantially smooth interior, whereby fluid under pressurecarried by said tubing string will not exert a significant tensile forceon said frangible portion 3. The safety joint of claim 1 wherein saidsupport means includes:

a plurality of segmented support members disposed in said groove inengagement with said body member; and

a sleeve member encircling a portion of said body member including saidgroove and engaging said support members to retain said support membersin said groove.

4. The safety joint of claim 1 wherein said body member has a secondannular groove proximate said first-mentioned annular groove forming anannular flange therebetween; and

said support means includes a plurality of segmented support membershaving an interior configuration mating with said annular grooves andsaid annular flange and engaging said body member to support saidfrangible portion against deformation by the fluid under pressure and tosupport said body member against compressive loads placed on said tubingstring, thereby avoiding bucking of said frangible portion, and

a sleeve member encircling a portion of said body member including saidgrooves, said sleeve member being connected with said body memberbetween said second annular groove and the end portion adjacent saidsecond annular groove and engaging said segmented support members tohold said support members in said grooves until said frangible portionparts and to retain said segmented support members in said secondannular groove at all times.

5. In a string of tubing or the like adapted to be disposed in a wellbore and to carry fluid under pressure, a safety joint connectable insaid tubing providing for the separation of the tubing upon applicationof a predetermined tensile force, said safety joint comprising:

a unitary tubular body member having first and second end portionsarranged for connection with the tubing string,

a first annular groove encircling the exterior thereof intermediate saidend portions forming a frangible portion and a downwardly facing annularabutment thereon, said frangible por tion having a predetermined tensilestrength whereby said safety joint will part in said frangible portionwhen a tensile force is exerted on said tubing string exceeding thestrength of said frangible portion,

a second annular groove encircling the exterior thereof proximate saidfirst annular groove forming an annular flange having an outer diameterless than the outer diameter of said body member and forming an upwardlyfacing annular abutment, and

a substantially smooth interior, whereby fluid under pressure carried bysaid tubing string will not exert a significant tensile force on saidfrangible portion;

a pair of hemi-cylindrical support members disposed in said annulargrooves, each of said support members being in engagement with saidupwardly and downwardly facing annular abutments to support said tubularbody against compressive forces exerted on said tubing string therebyavoiding compressive buckling of said frangible portion, each of saidsupport members including a pair of spaced inwardly directed flanges,one of said inwardly directed flanges being located in said firstannular groove in engagement with said frangible portion to support saidfrangible portion against deformation from the fluid pressure and theother inwardly directed flange being located in said second annulargroove in engagement with said annular flange; and

a sleeve member encircling a portion of said body member including saidgrooves and connected with said body member between said second annulargroove and the adjacent end portion, said sleeve member engaging saidsupport members to retain said suppoit members in said grooves untilsaid frangible portion parts and to retain said support members in saidsecond annular groove at all times.

6. In a string of tubing or the like adapted to be disposed in a wellbore and to carry fluid under pressure, a safety joint connectable insaid tubing providing means for the separation of the tubing upon theapplication of a predetermined tensile force, said safety jointcomprising:

a unitary tubular body member having first and second end portionsarranged for connection with the tubing string, and

an annular groove encircling the exterior thereof intermediate said endportions forming a frangible portion thereon, said frangible portionhaving a predetermined tensile strength whereby said safety joint willpart in said frangible portion when a tensile force is exerted on saidtubing string exceeding the strength of said frangible portion; and

support means at least partially disposed in said groove, said supportmeans engaging said tubular body member in said groove to support saidfrangible por- 7 tion against deformation by a force other than thepredetermined tensile force exerted on said body member.

References Cited UNITED STATES PATENTS 1,814,800 7/1931 Heater 285-21,936,669 11/1933 Heeter 285-3 2,048,388 7/1936 Johnsen 285-4 X Boyles85-61 Boynton 285-111 X Conrad et a1. 285-4 X Toelke 285-2 X EDWARD C.ALLEN, Primaly Examiner.

CARL W. TOMLIN, Examiner.

R. G. BERKLEY, Assistant Examiner.

